The present invention is directed to exposure apparatuses. More specifically, the present invention is directed to a support assembly for an exposure apparatus and a method for making a support assembly for an exposure apparatus that facilitates the disassembly of the major subassemblies of the exposure apparatus to allow for field servicing of the subassemblies.
Exposure apparatuses are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes a support assembly, a measurement subassembly, a control system, an illumination source having an illumination optical assembly, a projection optical subassembly, a reticle stage for retaining a reticle, and a wafer stage for retaining a semiconductor wafer.
The support assembly typically supports the measurement subassembly, the illumination optical subassembly, the projection optical subassembly, the reticle stage, and the wafer stage above the ground. The measurement subassembly monitors the positions of the stages. The wafer stage includes one or more motors to precisely position the wafer relative to the projection optical subassembly. Similarly, the reticle stage includes one or more motors to precisely position the reticle relative to the projection optical subassembly.
The feature sizes of the images transferred onto the wafer from the reticle are extremely small. Accordingly, the precise relative positioning of the wafer and the reticle is critical to the manufacture of high density, semiconductor wafers.
Unfortunately, mechanical vibrations and deformations can influence the accuracy of the exposure apparatus. For example, motors utilized in the reticle stage and the wafer stage generate reaction forces that vibrate the support assembly of the exposure apparatus. The vibrations in the support assembly can move the stages and the projection optical assembly out of precise relative alignment. Further, the vibrations in the support assembly can cause the measurement subassembly to improperly measure the relative positions of the stages. As a result thereof, the accuracy of the exposure apparatus and the quality of the integrated circuits formed on the wafer can be compromised.
Additionally, many of the subassemblies of the exposure apparatus require adjustment, modification and routine servicing that are preferably performed at the field site of the exposure apparatus. For example, the projection optical subassembly of an electron beam exposure apparatus may require the replacing of apertures and beam tubes which become contaminated by residues evaporated by the electron beam or other sources of hydrocarbons.
Unfortunately, many of these subassemblies are difficult to access and remove from the exposure apparatus. One attempt to solve this problem involves the use of an overhead crane to sequentially remove the subassemblies from the exposure apparatus. With this design, if a lower subassembly of the exposure apparatus needs to be removed, all of the upper subassemblies of the exposure apparatus must be removed before the crane can obtain access to the lower subassembly. Further, the overhead crane can take up a lot of space and can require a significant amount of clearance above the exposure apparatus. Exposure systems are normally installed in cleanrooms which have limited height. Moreover, during disassembly the operation of the overhead crane can create dust and other contaminants that can fall downward into the components of the exposure apparatus. The contaminants can influence the accuracy and performance of the components and the exposure apparatus.
In light of the above, there is a need for an improved support assembly for an exposure apparatus that provides a high degree of isolation from environmental disturbances to the projection optical subassembly and the measurement subassembly. Additionally there is a need for a support assembly that facilitates the easy access and/or removal of one or more of subassemblies of the exposure apparatus for field servicing. Further, there is a need for an exposure apparatus that can be disassembled without an overhead crane. Furthermore, there is a need for an exposure apparatus capable of manufacturing precision devices, such as high density, semiconductor wafers.
The present invention is directed to a support assembly for an exposure apparatus and an exposure apparatus that satisfies these needs. The exposure apparatus includes one or more subassemblies. The support assembly includes a frame assembly and an elevator assembly. The support assembly supports the one or more subassemblies above an isolation base. Uniquely, the elevator assembly lifts at least one of the subassemblies and a portion of the frame assembly relative to the isolation base. As a result of this design, the subassembly can be easily accessed or removed from the exposure apparatus without the use of an overhead crane for service, maintenance, and adjustment.
As provided herein, the exposure apparatus includes a support assembly, an illumination system, a projection optical subassembly, a measurement subassembly, and a stage mover assembly. In one embodiment, the support assembly includes a first frame that retains the illumination optical subassembly, a second frame that retains the projection optical subassembly and the measurement subassembly, a reaction frame that retains part of the stage mover assembly, and the elevator assembly. In this embodiment, the elevator assembly (i) selectively lifts the first frame and the illumination optical subassembly relative to the second frame and the isolation base, (ii) selectively lifts the second frame and the projection optical subassembly relative to the first frame and the isolation base, and (iii) selectively lifts part of the stage mover assembly relative to the first and second frames and the isolation base.
Additionally, the support assembly can include a first pivot and a second pivot. The first pivot allows a portion of the first frame and the illumination optical subassembly to pivot relative to the second frame and the isolation base. Similarly, the second pivot allows a portion of the second frame and the projection optical subassembly to pivot relative to the first frame and the isolation base.
In summary, the elevator assembly selectively lifts and moves the optical subassemblies and the frames relative to the isolation base. The elevator assembly also selectively lifts and moves part of the stage mover assembly relative to the isolation base. Further, the pivot assembly can be used to move and pivot the optical subassemblies and a portion of the frames relative to the isolation base. As a result of this design, both optical subassemblies can be removed relatively easily from the exposure apparatus. Further, with this design, the projection optical subassembly and the measurement subassembly are supported independently from the illumination optical subassembly. This is important because the isolation requirements of the projection optical subassembly and the measurement subassembly are typically greater than the isolation requirements of the illumination optical subassembly.
The present invention is also directed to an exposure apparatus, a device, a wafer, method for making a support assembly, a method for making an exposure apparatus, a method for making a device, and a method for manufacturing a wafer.